1. Field of the Invention
This invention relates to mounting arrangements for a vehicle engine, and more particularly to arrangements for mounting the front end of such engines.
2. Description of the Prior Art
Proper mounting of the front end of a vehicle engine, and particularly engines for heavy vehicles such as trucks, imposes multiple requirements which are not fully compatible. Thus, one requirement is to isolate as much as possible the engine vibrations from the frame and the remainder of the truck, particularly the truck cab and the instrumentation therein and the occupants thereof. A second requirement is to limit the lateral movement of the engine relative to the frame, particularly during turning movement of the vehicle and extreme chassis articulations.
The former requirement is more satisfactorily met by using a relatively soft elastomeric material which minimizes the transmission of vibrations, and particularly vibrations of low frequency which are associated with heavy engines operating at relatively low speeds. On the other hand, minimizing the lateral movement of the engine in the case of vehicle turns or extreme articulation is better achieved by using a relatively stiff elastomeric material.
In the prior art two types of engine mounting arrangements have been employed. In one type of mounting arrangement, referred to as a trunnion-type mount, an annular band of elastomeric material is interposed between a trunnion portion of the engine mounting structure and the supporting portion of the frame. In the second type, referred to as a biscuit-type mount, cylinders of elastomeric material are interposed between the bottom of the engine and the supporting cross member of the vehicle frame. In both cases it has been necessary to make a compromise between the optimum characteristics of the elastomeric material for purpose of minimizing transmission of vibrations, and particularly low frequency vibrations, and the optimum characteristics of the elastomeric material for the purpose of minimizing lateral movement of the engine. As a result of this compromise, neither objective is ideally achieved.
The mounting arrangement of the subject invention is designed to achieve both objectives in an optimum fashion without the necessity of the compromise associated with prior art mounting arrangements. The mounting arrangement of this invention makes it possible to utilize elastomeric material which is relatively soft and thereby minimizes the transmission of low frequency vibrations to the vehicle body and components thereof and, at the same time, to limit satisfactorily the amount of lateral motion of the engine under conditions of vehicle turning or extreme articulation. By the mounting arrangement of this invention, collateral benefits are achieved, such as the elimination of the need for additional noise control material on the vehicle body, minimizing of the amount of area of elastomeric material exposed to destructive environmental elements such as oil, gasoline and ozone, elimination of extensive bracing for body components which must remain in a set position, such as rear vision mirrors, and minimizing adverse effects on sensitive instrumentation in the vehicle cab.
It is an object of this invention to minimize transmission vibrations from the engine to the vehicle body and especially low frequency vibrations occurring when an engine, particularly a heavy duty engine, is operating at low speeds.
It is another object of this invention to minimize such vibrations and at the same time effectively limit lateral movement of the engine relative to the frame, particularly during vehicle turns or extreme chassis articulations.
It is a further object of this invention to provide an engine mounting arrangement which permits utilization of softer elastomeric material, thereby effectively reducing transmission of low frequency noise, while still effectively limiting lateral positional deviation of the engine.